NO. 1507. FRESH- WA TER A MPHIPODA— WECKEL. 5 7 



After comparing- a large number of the dentate and nondentate forms 

 1 find they differ only in this one feature, and at present it seems best 

 not to make this difference one of specific value; consequently, I have 

 made Hyalella Inermix synon3"mous with Jlyalella htilckerhockei'l. 



I have also compared Doctor Stebbing\s type specimens of Jlyalella 

 faxoni^ from Volcan Reventado, Costa Rica, with a number of speci- 

 mens of Hyalella hnickerhodverl and feel convinced that they belong 

 to the same species. The differences which are pointed out by Doctor 

 Stebbing between Hyalella fa,ron> and the nondentate forms of 

 Hyalella JinicJierhocJcer! are very slight and are differences which are 

 often found upon comparison of a number of specimens of the same 

 species. The principal difference between the two, as pointed out by 

 Doctor Stel)bing, is the presence of three setw on the inner plate of 

 the first maxillge of Hyalella faxonl instead of two. 1 have found 

 specimens, however, from Yellowstone National Park and also from 

 the Isle Royal, Lake Superior, which agree with Hyalella knicker- 

 hocket'i in every detail, but on which 1 found three sette on the inner 

 plate of the first maxilla'; consequently this distinction between the 

 two forms is not valid. 



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